This invention relates to apparatus for the radiotransmission of data between a radiotransmitting station and a radioreceiving station and more specifically, to the recognition of enabling codes capable of enabling the receiving station to recognise and to process transmitted data encoded according to a predetermined key.
It is known for radioreceivers to be provided with devices which recognise enabling codes to enable the radioreceiver to receive data transmitted through air. Generally, the enabling code is a sequence of bits, and follows a group of bits used to synchronise the receiver to the transmission frequency. In some cases, as a result of radio frequency disturbances or of interferences with other transmissions, these enabling codes are erroneously interpreted by the recognising device as other synchronisation signals, but out of phase with the true transmitted synchronisation signals transmitted. The result is that the radioreceiver is not longer capable of recognising and processing the data transmitted.